1. Field of the Invention
The invention relates to a clamping lock for a tensioning means, which comprises a housing and a comb element mounted in the housing. The housing comprises in this case two cheek parts arranged at a distance from each other, a stop web which extends between the cheek parts and a pivot spindle which likewise extends between the cheek parts. The comb element is pivotably mounted on the pivot spindle of the housing. Clamping locks of this type are used to adapt the length of the respective tensioning means to the respective fastening task while maintaining the respectively required tensioning forces.
2. Description of Related Art
Clamping locks of the type in question are typically used in combination with tensioning means which are in the form of belts, bands or ropes, are sufficiently pliable and are at the same time able to transmit the tensioning forces required in each case.
Known clamping locks, such as are described in WO 00/30487 for example, generally have a housing and a comb element which is mounted in the housing in an eccentrically pivotably movable manner. At the same time, the known clamping locks generally have a stop element which is arranged in such a way as to form a clamping slot between a stop surface of the stop element, which stop surface is arched outward in the direction of the comb element, and the outwardly arched circumferential surface of the comb element, the clear width of the clamping slot being determined by the pivoting position of the comb element. The arrangement of the pivot spindle of the comb element and the stop surface of the stop element are in this case selected in such a way as to restrict the clamping slot in the event of the comb element being pivoted counter to the direction of insertion of the tensioning element. In this way, when the clamping slot is opened wide, it is possible to insert the tensioning element into the clamping slot in a substantially force-free manner. As soon as the required tension is subsequently reached in the tensioning means, the tensioning means exerts a high normal force on the circumferential surface of the comb element. After the free end guided by the clamping lock has been relieved of the tensioning force, the tensioning element entrains the comb element, as a consequence of this force and the friction acting between the comb element and tensioning means, counter to the direction of insertion, so that the width of the clamping slot is minimised and the tensioning means is clamped-in between the circumferential surface of the comb element and the stop surface of the stop element. On account of the reaction forces prevailing in the tensioning means in the tensioned state, this clamping is maintained until the comb element is pivoted in the direction of insertion by an externally acting force and the width of the clamping slot is in this way widened again.
The known clamping locks have the problem that, on the one hand, the clamping force prevailing in the clamping slot is dependent on the friction prevailing between the comb element and the tensioning means. On the other hand, in many cases it proves difficult in the known clamping locks, in practice in particular in tensioning fastenings requiring high tensioning forces, to release the comb element from its clamping position in order to set the tensioning means free again.
In the case of a variant of a clamping lock that is likewise disclosed in WO00/30487, attempts have been made to eliminate these problems by forming a rim, around which a tensioning element is guided, at the trailing end, in the direction of insertion of the tensioning means, of the first outwardly arched circumferential surface portion of the comb element that is associated with the stop surface of the stop element. The circumferential surface portion adjoining the rim in the direction of insertion is in this case embodied in a flattened manner, so that the tensioning element is guided in a kinked course around the rim. At its end opposing the rim, the flattened circumferential surface portion merges with a second outwardly arched circumferential surface portion which opposes the first outwardly arched circumferential surface portion of the comb element.
A stop surface, which is formed on a further correspondingly embodied housing web of the known clamping lock, is associated with this second circumferential surface portion too. In this way, a double clamping of the tensioning means in the tensioning position is achieved, the clamping forces being especially high on account of the deflection of the tensioning means about the rim between the first outwardly arched circumferential portion and the flattened circumferential portion. Nevertheless, this has the drawback that inserting the tensioning means into the clamping lock is so awkward as to be hardly manageable under the rough conditions prevailing in the practice of a carrier, for example.
The latter aspect also applies in particular because, in the known clamping lock, a lever, via which the comb element can be pivoted from a clamping to a release position, can additionally be moulded onto the comb element. This lever extends over the width of the comb element so that it can be used to transmit sufficiently high forces. In order nevertheless to be able to guide the tensioning means through the clamping lock, an opening, through which the tensioning element must additionally be guided on its path through the clamping lock, is formed in the lever.
Furthermore, in order to increase the safety with which the tensioning means draws the comb element into the clamping gap, it is known to mould latching projections onto the circumferential surface of the comb element that enters into contact with the tensioning means. The latching projections reach into the tensioning means, which in the tensioned state rests tight against the clamping element, thus producing not only a frictionally engaged, but also a form-fitting connection between the tensioning means and comb element (US 2004/0163216 A1).
In addition to the awkward handling, a further drawback of the known clamping locks consists in the fact that they are, on account of the large number of components required for assembly thereof, technically complex and accordingly expensive to manufacture.
A clamping lock which can be produced more economically as a result of a reduction in the number of components required for manufacture thereof is known from EP 0 841 020 A1. This known clamping lock has a housing which is produced in one piece from plastics material and in which a separately pre-produced comb element, which is also made of plastics material, is pivotably mounted. The housing has two elongate cheeks arranged parallel and at a distance from each other. In the region of its one end, a stop web, around which the band, which is to be adjusted in each case with respect to its effective length, is loosely guided, extends between the cheeks, whereas a likewise web-like fastening portion extends in the region of its other end between the cheeks. The stop web is in this case traversed by a through-opening which is oriented coaxially with its longitudinal axis and with the inlet openings of which a lug of a bracket which is pivotably mounted on the stop web engages.
For pivotably mounting the comb element, in the clamping lock known from EP 0 841 020 A1, the plastics material housing contains a separately pre-produced spindle which is fed through two openings in the cheeks, which openings are arranged opposing each other and oriented coaxially with each other and axis-parallel to the longitudinal axis of the stop web. At the same time, the spindle is guided through a corresponding through-opening on an end portion of the comb element.
A drawback of the embodiment of a clamping lock as known from EP 0 841 020 A1 is the fact that the pivot spindle required for the comb element has to be inserted into the housing as a separate component. This not only requires a relatively small diameter of the spindle, but also necessitates the use of a material for the spindle which is able to withstand the forces occurring during practical use. In addition, the simultaneous insertion of the spindle through the openings associated therewith in the housing and the opening in the comb element requires an additional operation which has to be carried out at high precision.
Finally, GB 678,069 discloses a clamping lock which likewise comprises a housing produced in one piece from a material (not defined in greater detail) and a comb element which is pivotably mounted in the housing. The housing likewise has two lateral cheeks between the one ends of which a fastening portion extends for fastening the one end of the band which is in each case to be adjusted with respect to its effective length, whereas a stop web, via which the band is guided and against which a comb element which is pivotably mounted in the housing acts, is embodied between the other ends of the cheeks. The comb element is in this case pivotably mounted on two short lugs which protrude inward into the space bounded by the housing and reach into corresponding openings in the comb element. In the stress-relieved, non-deformed state, the width of the comb element corresponds, apart from a slight undersize, to the clear width between the cheeks of the housing.
The prerequisite for the assemblability and operativeness of the clamping lock known from GB 678,069 is accordingly that the comb element be flexible transversely to its pivot spindle to the extent that its openings can be brought into engagement with the lugs of the housing that are associated therewith in each case by an appropriate elastic deformation of the comb element or housing. Likewise, sufficient pliability of the comb element should also allow the known clamping lock to be used on bands of differing thickness. This deformability, which is thus necessarily present, harbours the risk that sufficient clamping of the band will no longer be ensured at high loads.
Against the background of the prior art described hereinbefore, the object of the invention consisted in providing a clamping lock which has high functional reliability and also a compact, easily manageable design and can at the same time be manufactured in a simple manner.